Battery pack and production method for same

ABSTRACT

A battery pack includes: a connector holder that is fixed to an exterior case and has two main surfaces that include a first main surface exposed through an opening of the exterior case; a floating connector connected with a center of the connector holder in such a manner that the floating connector floats in such a manner that an orientation or a position of the floating connector is variable upward, downward, leftward, and rightward; a lead wire fixed to an inner surface of the floating connector, the lead wire extending through an inside of the exterior case, and the lead wire connecting floating connector with a circuit board; and a positioning buffer that pushes the floating connector, and positions the floating connector at a predetermined original state when an external force is not applied to the floating connector.

TECHNICAL FIELD

The present invention relates to a battery pack and a production methodfor the battery pack.

BACKGROUND ART

Battery packs are widely used as power sources for electric tools,electric bicycles, electric motorcycles, hybrid electric vehicles, andelectric vehicles, for example. Further, battery packs are widely usedto store electricity at home and stores, for example. Such a batterypack includes a plurality of chargeable secondary-battery cellsconnected with each other in series and in parallel. Consequently, thebattery pack is chargeable and dischargeable. For example, batterymodule 80 includes battery holder 82 that holds a plurality of batterycells 81, as illustrated in FIG. 14 . Battery module 80 is disposed inwaterproof container 83. Waterproof container 83 that contains batterymodule 80 is a core pack of a battery. Waterproof container 83 thatcontains battery module 80 is disposed in exterior case 84. In batteryholder 82, the plurality of battery cells 81 are parallel to each other.Each of battery cells 81 has electrode terminals at both ends,respectively, of battery cell 81. In battery holder 82, the electrodeterminals of battery cells 81 are arranged on planes. Lead sheets 85 arearranged on two sides, respectively, of battery holder 82. Lead sheets85 connect the electrode terminals of battery cells 81 with each other.

Such a battery pack includes a connector used to electrically connectthe battery pack with a device to which the battery pack supplieselectrical energy. The device to which the battery pack supplieselectrical energy is a load. The connector may include a floatingmechanism that allows the connector to be easily connected with a deviceto which the battery pack supplies electrical energy (see PTLs 1 to 3,for example). The floating mechanism is a state in which the connectoris movable, and an orientation of the connector is slightly variable, asillustrated in a cross-sectional view of FIG. 15 . Consequently, aposition of the connector is vertically and laterally adjusted when theconnector is connected with a device to which the battery pack supplieselectrical energy. A lead wire electrically connects a battery modulewith a floating connector that includes such a floating mechanism.

Battery packs need to produce high power in recent years. Consequently,large electric current for charging or discharging flows through a leadwire of each of the battery packs. Therefore, diameters of the leadwires become larger. Consequently, the lead wires become less flexible.Consequently, the lead wire connected with the floating connector mayapply a force to the floating connector. For example, if the lead wireconnected with the floating connector is in some orientation, the leadwire may push the floating connector in one direction. Consequently, thelead wire may apply bias to the floating connector. Consequently,although the floating connector is used, the floating connector maybecome inclined from an original orientation. Further, even if thefloating connector is pushed from the original orientation, a restoringforce of the floating mechanism naturally allows the floating connectorto return to the original orientation. However, since the lead wire isfixed in an exterior case, the lead wire may push the floating connectorthat floats. Consequently, the floating connector may not return to theoriginal orientation. As described above, the lead wire connected withthe floating connector may interfere with part of a floating function.

CITATION LIST Patent Literature

PTL 1: WO 2016/072041 A1

PTL 2: Unexamined Japanese Patent Publication No. H2-51616

PTL 3: Unexamined Japanese Patent Publication No. 2013-14070

SUMMARY OF THE INVENTION

The present invention is made in view of the above background. It is anobject of the present invention to provide a battery pack that allows alead wire to be less likely to interfere with a floating function of afloating connector, and a production method for the battery pack.

A battery pack according to a first aspect of the present inventionincludes: a battery module that includes at least one secondary-batterycell; an exterior case that holds the battery module and has an opening;a circuit board electrically connected with the secondary-battery cellof the battery module; a connector holder that is fixed to the exteriorcase and has two main surfaces that include a first main surface exposedthrough the opening of the exterior case, and a second main surface thatis opposite the first main surface and faces an inside of the exteriorcase; a floating connector connected with a center of the connectorholder in such a manner that the floating connector floats in such amanner that an orientation or a position of the floating connector isvariable upward, downward, leftward, and rightward, the floatingconnector having an exposed surface exposed by the exterior case, andthe floating connector being able to be connected through the exposedsurface with a device to which the battery pack supplies electricalenergy; a lead wire fixed to an inner surface of the floating connectorthat is opposite the exposed surface of the floating connector, the leadwire extending through an inside of the exterior case, and the lead wireconnecting the floating connector with the circuit board; and apositioning buffer that pushes the floating connector, and positions thefloating connector at a predetermined original state when an externalforce is not applied to the floating connector.

Consequently, the floating connector is less likely to vertically move.Consequently, the floating connector is held at the original state.

A battery pack according to a second aspect of the present inventionincludes the configuration of the battery pack according to the firstaspect of the present invention. Further, in the battery pack accordingto the second aspect of the present invention, the positioning buffermay be a cushioning component that is between the connector holder andthe floating connector.

A battery pack according to a third aspect of the present inventionincludes the configuration of the battery pack according to the first orsecond aspect of the present invention. Further, in the battery packaccording to the third aspect of the present invention, the positioningbuffer may be at four corners between the connector holder and thefloating connector.

A battery pack according to a fourth aspect of the present inventionincludes the configuration of the battery pack according to any one ofthe first to third aspects of the present invention. Further, in thebattery pack according to the fourth aspect of the present invention,the connector holder may have a frame that surrounds the floatingconnector, and the positioning buffer may be on an inner surface of theframe.

A battery pack according to a fifth aspect of the present inventionincludes the configuration of the battery pack according to any one ofthe first to fourth aspects of the present invention. Further, in thebattery pack according to the fifth aspect of the present invention, thefloating connector may have a connector base on a back-surface side ofthe floating connector, and the positioning buffer may push theconnector base.

A battery pack according to a sixth aspect of the present inventionincludes the configuration of the battery pack according to any one ofthe first to fifth aspects of the present invention. Further, in thebattery pack according to the sixth aspect of the present invention, atape that has a smooth surface may be wound around the lead wire. In theconfiguration of the battery pack according to the sixth aspect of thepresent invention, the lead wire around which the tape is wound movesmore smoothly on the guide pipe. Consequently, frictional resistancedecreases. Consequently, the lead wire is less likely to push thefloating connector. Consequently, the lead wire is less likely tointerfere with a floating mechanism. Further, if a plurality of leadwires are used, the plurality of lead wires are tied into a bundle withthe tape. Consequently, the plurality of tied lead wires smoothly moveon the guide pipe.

A battery pack according to a seventh aspect of the present inventionincludes the configuration of the battery pack according to any one ofthe first to sixth aspects of the present invention. Further, in thebattery pack according to the seventh aspect of the present invention,the connector holder may have a fixing portion that allows the connectorholder to be inserted into the opening of the exterior case from aninside of the exterior case, and is used to fix the connector holder tothe opening of the exterior case from an inside of the exterior case.The configuration of the battery pack according to the seventh aspect ofthe present invention does not need a relay connector. The relayconnector is necessary if the connector holder is fixed to the exteriorcase from an outside of the exterior case. Therefore, the lead wire ispreliminarily welded to the floating connector. Then the lead wirewelded to the floating connector is directly connected with the circuitboard.

A battery pack according to an eighth aspect of the present inventionincludes the configuration of the battery pack according to any one ofthe first to seventh aspects of the present invention. Further, in thebattery pack according to the eighth aspect of the present invention,the connector holder may have a guide pipe on the second-main-surfaceside of the connector holder, the guide pipe may be cylindrical, and theguide pipe may surround the lead wire. In the configuration of thebattery pack according to the eighth aspect of the present invention,the lead wire passes through the guide pipe. Consequently, the guidepipe of the connector holder adjusts a position of the floatingconnector. Consequently, the floating connector is held at a center.Consequently, the lead wire is less likely to push the floatingconnector. Consequently, a floating function is less likely to beweakened. Consequently, the floating function is effective.Consequently, the battery pack is surely flexibly connected with adevice to which the battery pack supplies electrical energy.

A battery pack according to a ninth aspect of the present inventionincludes the configuration of the battery pack according to the first toeighth aspects of the present invention. Further, in the battery packaccording to the ninth aspect of the present invention, the lead wiremay be fixed to a center of the inner surface of the floating connector,and the lead wire may be perpendicular to the inner surface of thefloating connector.

A production method for a battery pack according to a tenth aspect ofthe present invention is a method for producing a battery pack. Thebattery pack includes: a battery module that includes at least onesecondary-battery cell; an exterior case that holds the battery moduleand has an opening; a circuit board electrically connected with thesecondary-battery cell of the battery module; a connector holder that isfixed to the exterior case and has two main surfaces that include afirst main surface exposed through the opening of the exterior case, anda second main surface that is opposite the first main surface and facesan inside of the exterior case; a floating connector connected with acenter of the connector holder in such a manner that the floatingconnector floats in such a manner that an orientation or a position ofthe floating connector is variable, the floating connector being able tobe connected with a device to which the battery pack supplies electricalenergy; and a lead wire that extends through an inside of the exteriorcase, and connects the floating connector with the circuit board.

The production method for a battery pack according to the tenth aspectof the present invention includes: arranging the battery module and thecircuit board in the exterior case; inserting the lead wire that extendsfrom the circuit board into the connector holder; connecting the leadwire that has been inserted into the connector holder with the floatingconnector; inserting the connector holder into the opening of theexterior case from an inside of the exterior case to fix, in a statewhere a positioning buffer is disposed between the connector holder andthe floating connector, and positions the floating connector at apredetermined original state when an external force is not applied tothe floating connector; and closing the exterior case.

Consequently, the positioning buffer is disposed in the connectorholder. Consequently, the floating connector is less likely tovertically move. Consequently, the floating connector is held at theoriginal state.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view that illustrates an appearance of a batterypack according to a first exemplary embodiment.

FIG. 2 is a back perspective view of an appearance of the battery packin FIG. 1 .

FIG. 3 is an exploded perspective view of the battery pack in FIG. 2 .

FIG. 4 is a cross-sectional view of the battery pack in FIG. 1 takenalong line IV-IV in FIG. 1 .

FIG. 5 is an enlarged cross-sectional view of main part that illustratesa floating connector of the battery pack in FIG. 4 .

FIG. 6A is a bottom view of the floating connector. FIG. 6B is a sideview of the floating connector. FIG. 6C is a plan view of the floatingconnector. FIG. 6D is a cross-sectional view of the floating connectorin FIG. 6B taken along line VID-VID in FIG. 6B.

FIG. 7 is an exploded perspective view that illustrates the floatingconnector in FIG. 5 .

FIG. 8 is a cross-sectional view that illustrates a positioning bufferaccording to a second exemplary embodiment.

FIG. 9 is a perspective view that illustrates the floating connector inFIG. 5 .

FIG. 10 is a plan view that illustrates the floating connector in FIG. 9.

FIG. 11 is an enlarged cross-sectional view of main part thatillustrates a floating connector of a battery pack according to a thirdexemplary embodiment.

FIG. 12A is a plan view that illustrates an example of a cut-offportion.

FIG. 12B is a plan view that illustrates another example of a cut-offportion.

FIG. 12C is a plan view that illustrates another example of a cut-offportion.

FIG. 13 is a cross-sectional view that illustrates a lead wire accordingto an example of modification.

FIG. 14 is an exploded perspective view that illustrates a conventionalbattery pack.

FIG. 15 is a cross-sectional view that illustrates an example of afloating connector according to a comparative example.

FIG. 16 is an enlarged perspective view that illustrates a floatingconnector fixed to an exterior case.

DESCRIPTION OF EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the drawings. However, the exemplaryembodiments described below are examples that allow a technical idea ofthe present invention to be embodied, and the present invention is notlimited to the exemplary embodiments described below. The presentdescription never limits components recited in the claims to componentsin the exemplary embodiments. It is especially intended that sizes,materials, and shapes of components, and arrangements of the componentsthat are described in the exemplary embodiments do not limit the scopeof the present invention, unless otherwise specified. The sizes,materials, and shapes of components, and arrangements of the componentsthat are described in the exemplary embodiments are mere examples forexplanation. Sizes of components and positional relation betweencomponents in each of the drawings may be exaggerated for clearexplanation. Furthermore, in the following description, same names orsame reference marks denote same components or same types of components,and detailed description is therefore appropriately omitted.Furthermore, one component may function as a plurality of elements ofthe present invention. Alternatively, a function of one component may beperformed by a plurality of components.

First Exemplary Embodiment

FIGS. 1 to 7 illustrate a battery pack according to a first exemplaryembodiment. FIG. 1 is a perspective view that illustrates an appearanceof battery pack 100 according to the first exemplary embodiment. FIG. 2is a back perspective view of an appearance of battery pack 100 in FIG.1 . FIG. 3 is an exploded perspective view of battery pack 100 in FIG. 2. FIG. 4 is a cross-sectional view of battery pack 100 in FIG. 1 takenalong line IV-IV in FIG. 1 . FIG. 5 is an enlarged cross-sectional viewof main part that illustrates floating connector 30 of battery pack 100in FIG. 4 . FIG. 6A is a bottom view of floating connector 30. FIG. 6Bis a side view of floating connector 30. FIG. 6C is a plan view offloating connector 30. FIG. 6D is a cross-sectional view of floatingconnector 30 in FIG. 6B taken along line VID-VID in FIG. 6B. FIG. 7 isan exploded perspective view that illustrates floating connector 30 inFIG. 5 .

(Exterior Case 40)

Exterior case 40 has a shape like a box. Exterior case 40 forms a shapeof battery pack 100 illustrated in FIGS. 1 and 2 . Exterior case 40 hasa space inside exterior case 40. Battery module 10 is disposed in thespace. Exterior case 40 is divided into lid 41 and main body 42, asillustrated in FIG. 3 . The main body has the space. Exterior case 40 ismade of a light material that has an excellent insulating property, suchas a resin. Exterior case 40 may have handle 43 on a top of exteriorcase 40, and legs 44 on a bottom of exterior case 40, as necessary.Further, exterior case 40 includes a charging terminal and a dischargingterminal in a surface of exterior case 40. In the example, exterior case40 includes charging terminal 45 in a top of exterior case 40, asillustrated in FIG. 1 . Further, exterior case 40 includes dischargingterminal 46 in a bottom of exterior case 40, as illustrated in FIG. 2 .The terminals may be each covered with a cover, such as a cap.Consequently, surfaces of the terminals are not exposed. In an examplein FIG. 1 , charging terminal 45 is covered. In the example, chargingterminal 45 and discharging terminal 46 are separate from each other.However, the present invention is not limited to the configuration. Thecharging terminal and discharging terminal 46 may be integrally made.

In examples in FIGS. 2 and 3 , exterior case 40 has depression 47 in asurface of exterior case 40. Floating connector 30 is disposed indepression 47. Consequently, floating connector 30 does not protrudefrom the surface of exterior case 40. Therefore, floating connector 30is not allowed to accidentally come into contact with an object.

Exterior case 40 includes opening 48, as illustrated in an explodedperspective view of FIG. 3 , and cross-sectional views of FIGS. 4 and 5. Connector holder 20 is fixed to opening 48. Floating connector 30 isdisposed in depression 47, as described above. Opening 48 is in a bottomof depression 47.

(Battery Module 10)

Battery module 10 is disposed in exterior case 40, as illustrated in across-sectional view of FIG. 4 . Battery module 10 includes at least onesecondary-battery cell 1. The secondary batteries are connected witheach other in series and in parallel. Consequently, battery module 10produces predetermined power, and has a predetermined capacity. Batterymodule 10 includes battery holder 11, as illustrated in an explodedperspective view of FIG. 3 . Battery holder 11 holds a plurality ofsecondary-battery cells 1. Secondary-battery cells 1 are eachcylindrical. Battery holder 11 includes cell retainers. The cellretainers retain ends of respective secondary-battery cells 1. The cellretainers are each cylindrical. When secondary-battery cells 1 aredisposed in battery holder 11, surfaces of ends of secondary-batterycells 1 are out of battery holder 11. The surfaces of ends are welded tolead sheets. The lead sheets connect secondary-battery cells 1 with eachother in series and in parallel. In an example in FIG. 3, 28secondary-battery cells 1 are connected with each other. Morespecifically, four parallel sets of seven secondary-battery cells 1 inseries are connected with each other. Shapes and an arrangement of thelead sheets depend on parallel and series connections ofsecondary-battery cells 1.

The lead sheets are made of a metal that has excellent conductivity. Thelead sheets are connected with surfaces of ends of secondary-batterycells 1 by spot welding, for example. The lead sheets are connected withcircuit board 3. Circuit board 3 is disposed on a side of battery holder11. Circuit board 3 includes a circuit that charges and dischargessecondary-battery cells 1, and a protection circuit.

Each of secondary-battery cells 1 is a cylindrical battery that includesa cylindrical exterior can. Secondary-battery cells 1 may be lithium-ionsecondary batteries, nickel metal hydride secondary batteries, ornickel-cadmium secondary batteries, for example. Lithium-ion secondarybatteries are especially preferable because lithium-ion secondarybatteries have high energy efficiency per unit of volume. The leadsheets connect electrodes of surfaces of ends of the plurality ofsecondary-battery cells with each other. Consequently, the plurality ofsecondary-battery cells are connected with each other in series and inparallel. The present invention is not limited to secondary-batterycells that are cylindrical. Prismatic (rectangular) batteries or pouchbatteries may be used.

If battery module 10 is disposed in a waterproof container, batterymodule 10 becomes waterproof. The waterproof container may be a bag. Thewaterproof bag is made of a transparent resin, such as polyethylene. Ifa waterproof function is not necessary for battery module 10, thewaterproof bag may be eliminated.

(Connector Holder 20)

Exterior case 40 exposes connector holder 20 through opening 48 ofexterior case 40. As illustrated in an enlarged cross-sectional view ofFIG. 5 , connector holder 20 is fixed to exterior case 40. Connectorholder 20 has two main surfaces. First main surface 21 is one of the twomain surfaces. First main surface 21 is exposed through opening 48 ofexterior case 40. Second main surface 22 is opposite first main surface21. Second main surface 22 faces an inside of exterior case 40.

(Floating Connector 30)

Floating connector 30 is attached to connector holder 20. Floatingconnector 30 is a terminal that is able to be connected with a device towhich battery pack 100 supplies electrical energy. In the example,floating connector 30 is a discharging terminal. More specifically,exterior case 40 exposes part of a surface of floating connector 30.Discharging terminal 46 is made or disposed on the exposed part of asurface of floating connector 30. If magnetism is used to connectfloating connector 30 with a device to which battery pack 100 supplieselectrical energy, a magnet or a metallic piece is attached todischarging terminal 46. The magnetic connection allows floatingconnector 30 to be positioned at an appropriate position. Further, themagnetic connection allows floating connector 30 to continue to beconnected with a device to which battery pack 100 supplies electricalenergy.

Floating connector 30 has connector base 32 on a back-surface side offloating connector 30. The back-surface side is an inner surface offloating connector 30 that is opposite the exposed part of a surface offloating connector 30. Connector base 32 has a shape like a disk, forexample. Lead wire 50 is connected with substantially a center ofconnector base 32. Lead wire 50 is fixed to substantially a center offloating connector 30. Lead wire 50 is substantially perpendicular tofloating connector 30. Lead wire 50 extends through an inside ofexterior case 40 and is connected with circuit board 3.

(Floating Mechanism)

Floating connector 30 is connected with connector holder 20 in such amanner that floating connector 30 floats in such a manner that X, Y, andZ axes and an angle of floating connector 30 are variable. FIG. 6A is abottom view of connector holder 20 connected with floating connector 30.FIG. 6B is a side view of connector holder 20 connected with floatingconnector 30. FIG. 6C is a plan view of connector holder 20 connectedwith floating connector 30. FIG. 6D is a cross-sectional view ofconnector holder 20 connected with floating connector 30. As illustratedin FIGS. 6A to 6D, connector holder 20 has frame 23 that is rectangular.Connector holder 20 is open on a first-main-surface-21 side (a bottomside) of connector holder 20. Therefore, floating connector 30 isexposed. Floating connector 30 is held in frame 23 in such a manner thatfloating connector 30 floats in such a manner that an orientation(=posture, or attitude) of floating connector 30 is slightly variable.That is to say, an angle of floating connector 30 is variable, and aposition of floating connector 30 is adjustable along X, Y, and Z axes.In an example in FIG. 5 , holding sheet 24 is fixed to an inner surfaceof frame 23. Holding sheet 24 is a flat sheet. Holding sheet 24 has anopening in a center of holding sheet 24. Floating connector 30 isdisposed in the opening. Connecting component 25 is between floatingconnector 30 and holding sheet 24. Connecting component 25 is flexible,and is a bellows or rubber, for example. Connecting component 25connects floating connector 30 with holding sheet 24. Since connectingcomponent 25 deforms, an orientation of floating connector 30 isvariable. As described above, floating connector 30 is not completelyfixed, but is allowed to slightly move. Therefore, when battery pack 100is connected with a device to which battery pack 100 supplies electricalenergy, a position of floating connector 30 relative to a connector ofthe device to which battery pack 100 supplies electrical energy isadjustable, and an orientation of floating connector 30 is adjustable.Therefore, battery pack 100 is surely connected with the device to whichbattery pack 100 supplies electrical energy.

Floating connector 30 is held by connector holder 20 in such a mannerthat floating connector 30 floats in such a manner that an orientationof floating connector 30 is variable. Further, preferably, floatingconnector 30 has a restoring force that allows floating connector 30 toreturn to an original state when an external force is not applied tofloating connector 30. When floating connector 30 is in the originalstate, preferably, floating connector 30 is held horizontally. That isto say, preferably, floating connector 30 is held substantially parallelto a bottom of exterior case 40, and floating connector 30 is held atsubstantially a center of the opening of holding sheet 24. Consequently,when battery pack 100 is connected with a device to which battery pack100 supplies electrical energy, floating connector 30 is easilyconnected with a connector of the device to which battery pack 100supplies electrical energy. In an example in FIG. 5 , floating connector30 is parallel to a plane of holding sheet 24.

Connector holder 20 and floating connector 30 may be standardizedcomponents. Consequently, a conventional floating connector thatincludes a lead wire becomes usable, and an orientation of theconventional floating connector becomes adjustable. Consequently, theorientation of the conventional floating connector is held at a centraloriginal orientation. In an example in FIG. 3 , connector holder 20 isstandardized and has depression 47. Further, floating connector 30 isstandardized and includes lead wire 50 connected with floating connector30. Floating connector 30 is disposed in depression 47.

In an example in FIG. 6A, frame 23 of connector holder 20 isrectangular. However, a frame may be cylindrical, for example.

(Positioning Buffer(s) 70)

Further, connector holder 20 contains positioning buffer(s) 70.Positioning buffer(s) 70 push(es) floating connector 30. Consequently,positioning buffer(s) 70 position(s) floating connector 30 at apredetermined original state when an external force is not applied tofloating connector 30. Since connector holder 20 contains positioningbuffer(s) 70, floating connector 30 is less likely to vertically move.Consequently, floating connector 30 is held at the original state.

Positioning buffer(s) 70 is/are made of a material that elasticallydeforms. Positioning buffer(s) 70 is/are a cushioning component(s) madeof rubber, urethane, or polyethylene foam, for example. Alternatively,positioning buffer 70 is a spring, such as a compression spring or aleaf spring. Such positioning buffer(s) 70 is/are disposed betweenconnector holder 20 and floating connector 30. In an example illustratedin an exploded perspective view of FIG. 7 , positioning buffers 70 arecolumnar cushioning components 71. Columnar cushioning components 71 arearranged at four corners, respectively, of a back surface of connectorholder 20. Columnar cushioning components 71 push four corners ofconnector base 32 of floating connector 30. Consequently, equal stressesact on floating connector 30 in four respective directions.Consequently, floating connector 30 becomes easily held horizontally.That is to say, floating connector 30 of the battery pack is less likelyto become out of a center. Further, floating connector 30 of the batterypack is less likely to become inclined. Consequently, a floatingfunction is less likely to be weakened. Further, an initial orientationof floating connector 30 is pushed toward a device to which the batterypack supplies electrical energy. Consequently, floating connector 30 ismore securely connected with a device to which the battery pack supplieselectrical energy.

Columnar cushioning components 71 each have a size that allows columnarcushioning components 71 to be arranged at four corners of a backsurface of connector holder 20, and allows columnar cushioningcomponents 71 to push connector base 32 of floating connector 30. In anexample in FIG. 7 , columnar cushioning components 71 are cylindrical.However, a shape of cushioning components is not only cylindrical, butalso may be a rectangular prism, a prism, or a sphere.

Second Exemplary Embodiment

Positioning buffer(s) 70 not only push(es) floating connector 30 in fourdirections, but also may push whole floating connector 30. In case offloating connector 30B according to a second exemplary embodimentillustrated in FIG. 8 , positioning buffer 70 is annular, for example.Annular cushioning component 72 pushes a back surface of connector base32 of floating connector 30B. Lead wire 50 is at substantially a centerof annular cushioning component 72. That is to say, inclination aroundlead wire 50 is allowed. A stress that annular cushioning component 72applies to floating connector 30B is always uniform in all directionsaround lead wire 50. Consequently, the stress more securely holdsfloating connector 30B at an original state. Instead of the annularcushioning component, an annular compression spring, or an annular wavewasher (leaf spring) may be used as the buffer.

(Guide Pipe 26)

Connector holder 20 is closed on a second-main-surface-22 side (a topside) of connector holder 20. Guide pipe 26 may connect withsubstantially a center of the second-main-surface-22 side of connectorholder 20. Guide pipe 26 is cylindrical. Frame 23 and guide pipe 26 aremade in such a manner that a space in frame 23 adjoins an inner surfaceof guide pipe 26. Frame 23 and guide pipe 26 are integrally made. Guidepipe 26 is fixed to second main surface 22 of connector holder 20. Guidepipe 26 is substantially perpendicular to second main surface 22 ofconnector holder 20. Lead wire 50 fixed to a back surface of connectorholder 20 is inserted in guide pipe 26. Consequently, lead wire 50 issubstantially vertically held. Therefore, lead wire 50 does not applybias to floating connector 30 connected with lead wire 50. If lead wire50 applies bias to floating connector 30, floating connector 30 becomesout of an original orientation of floating connector 30.

Hereinafter, a case will be described in which lead wire 50 connectedwith floating connector 30 interferes with the floating mechanism.Battery packs need to produce high power in recent years. Consequently,large electric current for charging or discharging flows through a leadwire of each of the battery packs. Therefore, resistances of the leadwires tend to become lower, and thus diameters of the lead wires tend tobecome larger. Consequently, the lead wires become less flexible.Consequently, a lead wire in some orientation or in some state may applya force to a floating connector. For example, a lead wire whose end isconnected with a floating connector may push or pull the floatingconnector. That is to say, although a floating connector is used, thefloating connector receives an external force from a lead wire connectedwith the floating connector. Consequently, the floating connector maybecome inclined from an original state, or may become out of a center.Further, even if an external force is applied to a floating connector, arestoring force of a floating mechanism naturally allows the floatingconnector to return to an original state after the external forcevanishes. For example, even if a floating connector is pushed, arestoring force of a floating mechanism naturally allows the floatingconnector to return to an original state after the floating connectorceases to be pushed. However, a lead wire may apply a force to thefloating connector, as described above. Consequently, the restoringforce is weakened. Consequently, the floating connector may not returnto the original state. As described above, a lead wire connected with afloating connector may interfere with a floating function.

In the present exemplary embodiment, however, connector holder 20 hasguide pipe 26 on a second-main-surface-22 side of connector holder 20,as illustrated in FIGS. 5, 9, and 10 . Guide pipe 26 is cylindrical andsurrounds lead wire 50. Guide pipe 26 is substantially perpendicular tothe second-main-surface-22 side. Consequently, lead wire 50 that extendsfrom an inner surface of floating connector 30 and extends substantiallyperpendicularly to the inner surface passes through guide pipe 26.Therefore, floating connector 30 is horizontally held. The lead wire isespecially less flexible near a connection between the lead wire and thefloating connector. Therefore, the floating connector is likely to beinfluenced by an angle of part of the lead wire that is near thefloating connector. For example, in a comparative example illustrated inFIG. 15 , there is no guide pipe, and lead wire 150 that connectsfloating connector 130 with a circuit board has a minimum lengthrequired to connect floating connector 130 with the circuit board. Inthat case, lead wire 150 is likely to become inclined. Consequently,floating connector 130 connected with an end of lead wire 150 is likelyto become inclined. In the present exemplary embodiment, guide pipe 26is disposed near a connection between lead wire 50 and floatingconnector 30, as illustrated in FIG. 5 . Guide pipe 26 holds lead wire50 in such a manner that part of lead wire 50 that is near theconnection is almost vertical. Consequently, an original state offloating connector 30 is almost horizontal. In other words, even if leadwire 50 applies a force to floating connector 30, guide pipe 26 adjustsan orientation of floating connector 30. Consequently, the orientationof floating connector 30 is horizontally held near the connectionbetween lead wire 50 and floating connector 30.

On the other hand, an inner diameter of guide pipe 26 is larger than anouter diameter of lead wire 50, as illustrated in FIGS. 5, 6D, and 9 .Consequently, guide pipe 26 does not interfere with the floatingmechanism of floating connector 30. Since an inner diameter of guidepipe 26 is larger than an outer diameter of lead wire 50, a space isformed around lead wire 50. Therefore, lead wire 50 is allowed toslightly move or deform in the space. Therefore, floating connector 30connected with lead wire 50 is allowed to become inclined. Therefore,the floating mechanism surely operates.

Third Exemplary Embodiment

The guide pipe that vertically holds the lead wire is not necessarilynecessary. Especially if the positioning buffer(s) described abovehorizontally hold(s) the floating connector, the guide pipe may beeliminated. The guide pipe is eliminated in a third exemplary embodimentillustrated in a cross-sectional view of FIG. 11 . In a battery pack inFIG. 11 , positioning buffer 70 is disposed between an inner surface ofconnector holder 20D and connector base 32D of floating connector 30D.Positioning buffer 70 holds floating connector 30D at an original state.Floating connector 30D at the original state is horizontal.

(Friction Decreasing Mechanisms)

On the other hand, if friction between a surface of lead wire 50 and aninner surface of guide pipe 26 is high, lead wire 50 may becomeimmovable. Consequently, floating connector 30 may not become inclined.Therefore, preferably, friction decreasing mechanisms are disposed thatdecrease friction between a surface of lead wire 50 and an inner surfaceof guide pipe 26. In an example illustrated in FIGS. 9 and 10 , cut-offportion 27 is an example of the friction decreasing mechanisms. A shapeof a cross section of guide pipe 26 that is cylindrical is a circle thathas cut-off portion 27. Such a configuration decreases an area of partof a surface of lead wire 50 that is in contact with an inner surface ofguide pipe 26 through which lead wire 50 passes. That is to say, if alead wire whose cross section is circular is in contact with a guidepipe whose cross section is circular, a curved surface of the lead wireis in contact with a curved surface of the guide pipe. Therefore, anarea of part of a surface of the lead wire that is in contact with aninner surface of the guide pipe is likely to increase. Cut-off portion27 of guide pipe 26 decreases an area of part of a surface of the leadwire that is in contact with an inner surface of the guide pipe.Therefore, frictional resistance is decreased.

Ribs 28 may be made on cut-off portion 27. Ribs 28 reinforce guide pipe26. In an example illustrated in FIGS. 9 and 10 , three ribs 28 outwardprotrude from cut-off portion 27. Guide pipe 26 has a circular crosssection. In a plan view, ends of ribs 28 are along the circular crosssection. Consequently, guide pipe 26 that has cut-off portion 27 becomesstrong.

Preferably, an edge of cut-off portion 27 has a radius of curvature thatis larger than a radius of curvature of a circular cross section ofguide pipe 26. For example, a surface of an end of cut-off portion 27Aof guide pipe 26A has a shape like a straight line whose radius ofcurvature is infinity, as illustrated in FIG. 12A. Consequently, an areaof part of a surface of the lead wire that is in contact with an innersurface of guide pipe 26A is smaller than an area of part of a surfaceof the lead wire that is in contact with an inner surface of a guidepipe that is circular. The present invention is not limited to a cut-offportion that has a shape like a straight line. A cut-off portion may becurved. For example, guide pipe 26B has cut-off portion 27B that iscurved, as illustrated in FIG. 12B. Even in that case, an area of partof a surface of the lead wire that is in contact with an inner surfaceof guide pipe 26B is smaller than an area of part of a surface of thelead wire that is in contact with an inner surface of a guide pipe thatis circular. Guide pipe 26B provides a space where lead wire 50 is ableto move. The space is larger than a space where lead wire 50 is able tomove provided by a guide pipe that has a cut-off portion that has ashape like a straight line. Therefore, floating connector 30 is allowedto become more inclined.

In FIG. 12B, the cut-off portion is convex. Alternatively, a cut-offportion may be concave, as illustrated in FIG. 12C. That is to say,cut-off portion 27C may be concave, and may protrude toward an inside ofa cylindrical shape of guide pipe 26. In that case, a radius ofcurvature of cut-off portion 27C is smaller than a radius of curvatureof a circle of guide pipe 26. However, an area of part of a surface ofthe lead wire that is in contact with an inner surface of guide pipe 26Cis even smaller than an area of part of a surface of the lead wire thatis in contact with an inner surface of guide pipe 26.

Preferably, a position of cut-off portion 27 depends on a position ofcircuit board 3 to which lead wire 50 is fixed. For example, an edge ofguide pipe 26 has cut-off portion 27 at a position of the edge that isfar from circuit board 3. The configuration especially allows a lengthof lead wire 50 to be longer than a minimum length required to connectfloating connector 30 with circuit board 3. Consequently, lead wire 50becomes easily handled. Consequently, assembly becomes more efficient.Further, lead wire 50 is allowed to deform more. Consequently, floatingconnector 30 becomes surely likely to be inclined. On the other hand, ifthe lead wire becomes longer, a length of the lead wire is longer than aminimum length required to connect the floating connector with thecircuit board. That is to say, the lead wire is curved. In that case,part of the lead wire is in contact with an inner surface of the guidepipe in a direction in which the lead wire is curved. An edge of guidepipe 26 has cut-off portion 27 at a position of the edge that is farfrom circuit board 3. Consequently, lead wire 50 is in contact withcut-off portion 27. Cut-off portion 27 decreases an area of part of asurface of lead wire 50 that is in contact with an inner surface of theguide pipe. Consequently, lead wire 50 smoothly moves on an innersurface of the guide pipe.

Preferably, cut-off portion 27 is parallel to an edge of circuit board3. For example, cut-off portion 27A is parallel to an edge of circuitboard 3, as illustrated in FIG. 12A. Preferably, cut-off portion 27 isinclined in a direction in which lead wire 50 extends from circuit board3, as illustrated in FIG. 10 . In FIG. 10 , lead wire 50 is connectedwith circuit board 3 at a left side of a top of circuit board 3. Leadwire 50 rightward extends from circuit board 3. Further, lead wire 50 iscurved in a shape like a letter “U”. Further, lead wire 50 is connectedwith floating connector 30. That is to say, lead wire 50 rightwardextends from circuit board 3. Further, lead wire 50 is curved, and isconnected with floating connector 30. In case of the configuration, leadwire 50 is likely to be in contact with a right inner surface of guidepipe 26. Further, as described above, lead wire 50 is long. Therefore,lead wire 50 that extends from circuit board 3 passes guide pipe 26.Further, lead wire 50 is curved, and is connected with floatingconnector 30. In that case, lead wire 50 is likely to be in contact withan upper inner surface of guide pipe 26. In light of the abovedescription, cut-off portion 27 is likely to be in contact with an upperside and a right side of guide pipe 26. Therefore, the cut-off portionis inclined in a direction in which lead wire 50 extends from circuitboard 3. For example, the cut-off portion is inclined downward toward aright in FIG. 10 . In the above description, however, the cut-offportion is parallel to an edge of circuit board 3. Consequently, cut-offportion 27 is positioned in such a manner that lead wire 50 that extendsfrom circuit board 3 rubs against cut-off portion 27. Consequently, leadwire 50 is surely in contact with cut-off portion 27. Consequently, leadwire 50 smoothly moves on the guide pipe. Consequently, floatingoperation becomes smooth.

(Tape 52)

Another example of the friction decreasing mechanisms is tape 52 thathas a smooth surface. Tape 52 may be wound around lead wire 50, asillustrated in a cross-sectional view of FIG. 13 . Consequently,frictional resistance of a surface of lead wire 50 decreases. Therefore,floating operation is more reliable. Tape 52 is made of a material thathas a low coefficient of friction, such as polypropylene.

Lead wire 50 includes not only one lead wire, but also may include aplurality of lead wires. The plurality of lead wires may be made ofdifferent materials. Further, the plurality of lead wires may havedifferent thicknesses. In that case, the plurality of lead wires aretied into a bundle with tape 52. Consequently, the plurality of leadwires are easily handled in exterior case 40. Consequently, assembly andmaintenance become more efficient. Further, tape 52 is wound around partof lead wire 50 that is in contact with guide pipe 26. Consequently,lead wire 50 smoothly moves on guide pipe 26, as described above.Consequently, frictional resistance decreases. Consequently, floatingconnector 30 is allowed to surely become inclined.

(Fixing Portions 29)

Connector holder 20 also has fixing portions 29 that allow connectorholder 20 to be inserted into opening 48 of exterior case 40 from aninside of exterior case 40, and are used to fix connector holder 20 toopening 48 of exterior case 40 from an inside of exterior case 40.Consequently, a relay connector is not necessary. The relay connector isnecessary if connector holder 20 is fixed to exterior case 40 from anoutside of exterior case 40. Therefore, lead wire 50 is preliminarilywelded to floating connector 30. Then lead wire 50 welded to floatingconnector 30 is directly connected with circuit board 3.

In an enlarged perspective view of FIG. 16 , floating connector 130 isdirectly fixed to exterior case 140 from an outside of exterior case140. Floating connector 130 is directly fixed to exterior case 140 withscrews 160. In that case, a relay connector is necessary to electricallyconnect a lead wire in exterior case 140. Consequently, a costincreases. If a battery pack needs to produce high power and largeelectric current flows, a connector for large electric current isnecessary. If a battery pack needs to be waterproof, a waterproofconnector is used. Consequently, a cost further increases. In thepresent exemplary embodiment, fixing portions 29 are used to fixconnector holder 20 to exterior case 40 from an inside of exterior case40. Therefore, such a relay connector is not necessary. Further,exterior case 40 is assembled in a last step of assembly. Therefore, theassembly becomes efficient. Known structures for fixing areappropriately used for fixing portions 29. For example, screw holes areused to screw connector holder 20 to exterior case 40 from an inside ofexterior case 40 with screws 60, as illustrated in FIG. 3 .

(Production Method for Battery Pack 100)

Finally, a production method for battery pack 100 will be described.First, battery module 10 and circuit board 3 are arranged in exteriorcase 40. Lead wire 50 extends from circuit board 3. Lead wire 50 isinserted into connector holder 20. Then lead wire 50 that has beeninserted into connector holder 20 is connected with floating connector30. Then connector holder 20 is inserted into opening 48 of exteriorcase 40 from an inside of exterior case 40. Then connector holder 20 isfixed to opening 48 of exterior case 40 from an inside of exterior case40. When connector holder 20 is fixed to opening 48 of exterior case 40from an inside of exterior case 40, positioning buffer(s) 70 has/havebeen disposed between connector holder 20 and floating connector 30.Then exterior case 40 is closed. Since positioning buffer(s) 70 is/aredisposed in connector holder 20, floating connector 30 is less likely tovertically move. Consequently, floating connector 30 is held at anoriginal state.

INDUSTRIAL APPLICABILITY

A battery pack and a production method for a battery pack according toan aspect of the present invention are suitably used as power sourcesfor electric tools, electric bicycles, electric motorcycles, hybridelectric vehicles, and electric vehicles. Further, the battery pack andthe production method for a battery pack according to an aspect of thepresent invention are suitably used as power sources used to storeelectricity at home and stores.

The invention claimed is:
 1. A battery pack comprising: a battery modulethat includes at least one secondary-battery cell; a lead sheet thatconnects the at least one secondary-battery cell in series and/or inparallel; an exterior case that holds the battery module and has anopening; a circuit board electrically connected with the lead sheet; aconnector holder that is fixed to the exterior case and has two mainsurfaces that include a first main surface exposed through the openingof the exterior case, and a second main surface that is opposite thefirst main surface and faces an inside of the exterior case, wherein theconnector holder has a guide pipe on a side of the second main surfaceof the connector holder; a floating connector connected with a center ofthe connector holder in such a manner that the floating connector floatsin such a manner that an orientation or a position of the floatingconnector is variable upward, downward, leftward, and rightward, thefloating connector having an exposed surface exposed by the exteriorcase, and the floating connector being able to be connected through theexposed surface with a device to which the battery pack supplieselectrical energy; a lead wire fixed to an inner surface of the floatingconnector that is opposite the exposed surface of the floatingconnector, the lead wire extending through an inside of the exteriorcase, and the lead wire connecting the floating connector with thecircuit board, wherein the lead wire passes through the guide pipe; anda positioning buffer that is disposed between the connector holder andthe floating connector, pushes the floating connector, and positions thefloating connector at a predetermined original state when an externalforce is not applied to the floating connector.
 2. The battery packaccording to claim 1, wherein the positioning buffer is a cushioningcomponent that is disposed between the connector holder and the floatingconnector.
 3. The battery pack according to claim 1, wherein thepositioning buffer is disposed at four corners.
 4. The battery packaccording to claim 1, wherein the connector holder has a frame thatsurrounds the floating connector, and the positioning buffer is disposedon an inner surface of the frame.
 5. The battery pack according to claim4, wherein the floating connector has a connector base on a back-surfaceside of the floating connector, and the positioning buffer pushes theconnector base.
 6. The battery pack according to claim 1, wherein a tapethat has a smooth surface is wound around the lead wire.
 7. The batterypack according to claim 1, wherein the connector holder has a fixingportion that allows the connector holder to be inserted into the openingof the exterior case from an inside of the exterior case, and is used tofix the connector holder to the opening of the exterior case from aninside of the exterior case.
 8. The battery pack according to claim 1,wherein the guide pipe is cylindrical.
 9. The battery pack according toclaim 8, wherein the lead wire is fixed to a center of the inner surfaceof the floating connector, and the lead wire is perpendicular to theinner surface of the floating connector.
 10. A production method for abattery pack, the battery pack including: a battery module that includesat least one secondary-battery cell; a lead sheet that connects the atleast one secondary-battery cell in series and/or in parallel; anexterior case that holds the battery module and has an opening; acircuit board electrically connected with the lead sheet; a connectorholder that is fixed to the exterior case and has two main surfaces thatinclude a first main surface exposed through the opening of the exteriorcase, and a second main surface that is opposite the first main surfaceand faces an inside of the exterior case, wherein the connector holderhas a guide pipe on a side of the second main surface of the connectorholder; a floating connector connected with a center of the connectorholder in such a manner that the floating connector floats in such amanner that an orientation or a position of the floating connector isvariable, the floating connector being able to be connected with adevice to which the battery pack supplies electrical energy; and a leadwire that extends through an inside of the exterior case, and connectsthe floating connector with the circuit board, the production method fora battery pack comprising, arranging the battery module and the circuitboard in the exterior case, inserting the lead wire that extends fromthe circuit board into the guide pipe of the connector holder,connecting the lead wire that has been inserted into the guide pipe ofthe connector holder with the floating connector, inserting theconnector holder into the opening of the exterior case from an inside ofthe exterior case to fix, in a state where a positioning buffer isdisposed between the connector holder and the floating connector, andpositions the floating connector at a predetermined original state whenan external force is not applied to the floating connector, and closingthe exterior case.